Which Marantz SR ??

I'm in the market for a new Marantz AVR and there are so many older SR models . If I get a 4K TV / 4K Blu Ray player in the next few of years do I need a 4K pass through Receiver? Or is that all going to change ....


Been looking at : 

SR5006 - 10
SR 6006-10
SR 7006-10

what do you think is the best value and will last with he advent of 4K ....I really only need 5.1 or 7.1 at most 
thanks!